1. Field of the Invention
The present invention relates to a method of fabricating an organic light emitting display and, more particularly, to a method of forming an organic layer pattern using a laser irradiation apparatus with a spatial light modulator when forming the organic layer pattern using a laser induced thermal imaging (LITI) method.
2. Description of the Related Art
In general, an organic light emitting display, which is a flat panel display, includes an anode electrode, a cathode electrode, and organic layers between the anode electrode and the cathode electrode. The organic layers include at least an emission layer. The organic layers may further include a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer, in addition to the emission layer. The organic light emitting display may be classified into a polymer organic light emitting display and a small molecule organic light emitting display depending on the organic layer, particularly, a material that forms the emission layer.
In order to implement full color in the organic light emitting display, it is required to pattern the emission layer. A method of patterning the emission layer includes a method using a shadow mask in the small molecule organic light emitting display, and an ink-jet printing method or a laser induced thermal imaging (hereinafter, referred to as LITI) method in the polymer organic light emitting display. With the LITI method, it possible to finely pattern the organic layer. The LITI method is usable for a large-sized display and is advantage in high resolution. Advantageously, the LITI method is a dry process, unlike the ink-jet printing that is a wet process.
The method of forming the organic layer pattern using such an LITI method needs at least a laser generator, an organic light emitting display substrate, and a donor substrate. A laser beam from the laser generator is absorbed by a light-to-heat conversion layer of the donor substrate and is converted to thermal energy, which allows a material forming a transfer layer to be transferred onto the substrate, thus patterning the organic layer on the substrate. This is disclosed in Korean Patent Application No. 1998-51844 and U.S. Pat. Nos. 5,998,085, 6,214,520 and 6,114,088.
In order to form the organic layer pattern, it is required to homogeneously adjust the laser beam, namely, incident light and to pattern the organic layer into a desired shape. For these reasons, a beam homogenizer such as Fresnel lens is used. In this case, however, the beam homogenizer works only for a prescribed type of incident light, not for other various types of incident light.